30 spf sunscreen or moisturizer with spf 45?

im on retin-a (at night) and duac gel (daytime). my skin is excessively oily and i have cystic acne. i am also taking the birth control microgestin (my acne might be hormonal, says OB-GYNE). i was advised to use sunscreen on face bec. of retin-a use. i bought aveeno sunscreen for the face with spf 30 (yellow bottle/tube), and i also bought neutrogena healthy defense moisturizer with spf 45. i dont know which to use, the one that acts primarily as sunscreen but lower spf, or the moisturizer but has a higer spf? i dont know if i need a moisturizer bec. my skin hasnt been drying out unlike other people's experience with retin-a. (i repeat, my skin is still oily)ive tried using both alternately but havent broken out so far. but i tan easily (i dont think i burn, i am a medium-complexioned, filipina)thanks for any input!